In the past, electromagnetically actuated valves have been designed for opening and closing mechanisms that combine the action of springs with electromagnets. For example, in U.S. Pat. No. 4,614,170 issued to Pischinger, it is disclosed to use springs in an electromagnetically actuated valve to switch from an open position to a closed position and vice-versa. In these valves, the core lies at a center equilibrium position between two electromagnets. To close the valve, a first electromagnet is energized, attracting the core to the first electromagnet and compressing a spring. To open the valve, the energized first electromagnet is turned off and the second electromagnet is energized. Due to the force of the pre-stressed spring, the core is accelerated toward the second electromagnet, thereby reducing the amount of magnetic force required to attract the core away from the first electromagnet.
One problem with the earlier valve designs was that the moving core did not operate quickly enough to open and close the valves with sufficient speed, force, or stroke required for the opening and closing of an internal combustion engine's intake and exhaust valves, or for the force and stroke required for gas compressors. Therefore, a need existed for a valve design that provided an efficiently designed moving core assembly that could be accelerated quickly enough for the desired applications, such as the modern internal combustion engine.
Another problem encountered with the design of electromagnetically actuated valves is in obtaining the precise mechanical tolerances required to achieve a zero gap at the upper electromagnet when the valve is properly seated. This problem is exacerbated by the thermal expansion that occurs during operation of the valve, in that the valve stem of an electromagnetic actuator typically lengthens due to heat expansion. When the valve closes, the pole face of the moving core element contacts the upper electromagnet, but due to the increased length in the valve stem, the valve may not be seated properly. Alternatively, the valve may be seated before the armature element reaches the upper electromagnet, preventing the valve from obtaining a zero gap. A zero gap is desired to maintain power consumption at a low level, and therefore, the valve is not operating at a desired efficiency level.
Another problem with the previously designed valves is that the moving core assembly must return to an initial neutral position when not in operation. The initial neutral position of the core element must be equidistant from both the first electromagnet and the second electromagnet. As previously described, it is known to use a spring to bias the core assembly in this neutral position. However, spring tensions inevitably vary, which creates difficulty in obtaining a neutral position for the core element that is centered between the electromagnets.
The present invention is directed to overcoming one or more of the problems set forth above.